Method for assembling conductive segments of a rotor winding or stator winding in a rotary electric machine

ABSTRACT

The inventive method of assembling conductive segments ( 16 ) of a rotor winding or a stator winding in a rotary electric machine comprises the following stages: insertion of the conductive segments ( 16 ) into slots made in a core ( 12 ) of the rotor or stator, whereby the free ends of the conductive segments protrude beyond the latter, and welding of the free ends of the conductive segments in groups of two in order to form a winding ( 14 ) around the rotor or stator. The conductor statements are both made of wire which is electrically conductive and coated with an electrically insulating material. The coating of electrically insulating material is removed in the welding zone of the conductive segments by the means used for welding the latter. The invention can be used for conducting segments of a rotor or stator winding in an alternator in a motor vehicle.

FIELD OF THE INVENTION

[0001] The present invention relates to a process for assemblingconductive segments of a rotor or stator winding of a rotary electricalmachine.

[0002] More particularly, the invention concerns a process forassembling conductive segments of a rotor or stator winding of amotor-vehicle alternator.

PRIOR ART

[0003] In a conventional configuration, the stator windings of amotor-vehicle alternator are formed by using pre-formed conductivewinding segments in the form of a U, which are inserted, by their base,into slots formed in a core of the stator in such a way that themutually opposite free-end zones of the conductive segments projectbeyond the latter, and by welding the conductive segments in pairs toform continuous wound components around the core.

[0004] An assembly technique of this kind is described, for example, inthe document EP-A-1 043 828. According to this technique, the conductivesegments are generally welded using arc-type welding, e.g. of the TIGtype, by creating a discharge between an electrode and the respectivefree end zones of the segments.

[0005] Since the conductive segments are generally formed by a wire ofelectrically conductive material, e.g. copper, covered by a layer ofelectrically insulating material, e.g. enamel, it is often desirable toprotect the insulating covering from the heat released during welding.To this end, use is generally made of a striking voltage that variesintermittently, such that the arcs produced by the voltage pulses areapplied in respective zones of the welding zones. This limits thequantity of heat released outside the welding zones. Since thistechnique gives rise to uncontrolled transient states during thestriking of the arcs, the use of a protection element inserted betweentwo end zones of two adjacent segments to be welded in such a way as toprotect the rest of the conductive segments has been proposed.

[0006] Thus, according to the technique described in the above-mentioneddocument, a protective chuck gripping the conductive elements to bewelded in such a way that, on the one hand, the heat released duringwelding does not spoil the layer of electrically insulating materialbetween the welding zones and, on the other hand, the heat is conductedtowards zones that are to be welded so as to produce preliminarypreheating.

[0007] However, this technique has one major disadvantage, inasmuch asit requires preliminary stripping of the free ends of the conductivesegments to be welded, considerably increasing the costs of production,and is difficult to envisage in high-speed production lines inasmuch asthe stripping operation takes a relatively long time.

[0008] Moreover, when the stripping stage is performed mechanically, inorder to completely remove the layer of electrically insulatingmaterial, the peripheral surface of the conductive wire is inevitablycut, leading to a reduction in the useful cross section of theconductive segments.

OBJECT OF THE INVENTION

[0009] The aim of the invention is to overcome these disadvantages.

[0010] Its object is therefore a process for assembling conductivesegments of a rotor or stator winding of a rotary electrical machine,comprising the stages consisting in:

[0011] inserting the conductive segments in slots arranged in a core ofthe rotor or of the stator in such a way that the segments projectbeyond the latter by their free ends,

[0012] folding the free ends of the conductive segments, and

[0013] welding the conductive segments in pairs by their projecting freeends to form a winding around the rotor or the stator,

[0014] essentially characterised in that, the conductive segments eachbeing formed by a wire of electrically conductive material covered witha layer of electrically insulating material, the layer of electricallyinsulating material is eliminated, in the zone in which the conductivesegments are welded, by the means used to weld the latter.

[0015] It is thus no longer necessary to provide a preliminary strippingstage, such as, for example, mechanical stripping of the layer ofelectrically insulating material. Moreover, the outlay incurred for theassembly of the segments is considerably reduced. The solution is thusrapid, simple and economical.

[0016] Surprisingly, it has furthermore been found that when the weldingprocess used is a welding process of the electron-beam or laser type,welds of very high quality can be achieved without carrying outpreliminary stripping of the conductive segments or welding in thepresence of residues of electrically insulating materials when apreliminary stage of partial stripping is implemented, that is to saywithout spoiling the conductive wire.

[0017] This assembly process can likewise include one or more of thefollowing characteristics, taken in isolation or in any of thetechnically possible combinations:

[0018] the stage in which the layer of electrically insulating materialis eliminated is carried out during the welding of the conductivesegments;

[0019] following the welding of the conductive segments, a stage inwhich debris of electrically insulating material produced during weldingis removed is carried out;

[0020] the stage of removing debris includes a phase in which the weldedzones are brushed, followed by a suction phase;

[0021] the welding process is a welding process of the electron-beamtype;

[0022] the general axis of the electron beam is inclined by about 45° tothe axis of the rotor or of the stator.

[0023] in the course of welding, the electron beam has imparted to it asweeping motion over the entire welding zone.

[0024] the welding process is an accurate and rapid laser-weldingprocess which makes it possible to obtain penetrating seams of highgeometrical accuracy.

[0025] the welding means is driven in a sequential manner; the laserbeam being switched on and then off alternately between each weldingoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other aims, characteristics and advantages of the invention willemerge from the following description, which is given purely by way ofexample, with reference to the attached drawings, in which:

[0027]FIG. 1 is a perspective view of a portion of a stator of amotor-vehicle alternator provided with a winding produced in accordancewith the invention;

[0028]FIG. 2 is a cross section through a portion of the stator in FIG.1;

[0029]FIG. 3 is a schematic view of the stator in FIG. 1 on a largerscale;

[0030]FIG. 4 is a view of the point of impact of the laser beam on thefree ends to be welded of the conductive segments;

[0031]FIGS. 5 and 6 are views similar to FIGS. 1 and 2 respectively of asecond embodiment example;

[0032]FIG. 7 is a partial plan view of the conductive-segment ends to bewelded in this second embodiment example;

[0033]FIG. 8 is a view similar to FIG. 7 after welding;

[0034]FIG. 9 is a partial perspective view of the welded ends of thesecond embodiment example;

[0035]FIG. 10 is a variant of FIG. 3 corresponding to a third embodimentexample of the invention, showing in plan view the path of the laserbeam relative to the ends to be welded;

[0036]FIG. 11 is a view similar to FIG. 4 of the third embodimentexample in FIG. 10;

[0037]FIG. 12 is a view similar to FIG. 8 of a fourth embodiment exampleof the invention;

[0038]FIGS. 13 and 14 are views similar to FIG. 8 of a fifth and a sixthembodiment example of the invention, respectively.

PREFERRED EMBODIMENT EXAMPLES OF THE INVENTION

[0039] In the explanation which follows, the assembly of a statorwinding of a motor-vehicle alternator will be described. However, theinvention also applies, where appropriate, to the assembly of a rotorwinding of an alternator and, in a general way, to the assembly of arotor or a stator of a rotary electrical machine.

[0040] As is known, a conventional motor-vehicle alternator includes arotor firmly fixed to a rotor shaft, the axial ends of which aresupported in rotation by a hollow support designed to be mounted on afixed part of the motor vehicle. On the inside, at its outer periphery,this support carries a stator, described below, surrounding the rotor.In this alternator, the rotor is shaped to form an inductor, while thestator is shaped to form an armature.

[0041] The support includes two parts, referred to respectively as afront bearing and a rear bearing. Each bearing features a centralreceptacle for mounting a ball bearing, in which the relevant end of therotor shaft is mounted. This shaft extends outside the front bearing inorder to support a drive member, conventionally a pulley, for drivingthe rotor in rotation by means of the heat engine of the vehicle, via amotion transmission device conventionally including at least one belt.As described, for example, in the document FR-A-2 806 224, filed on Sep.3, 2001, the alternator can be of the reversible type and can form astarter for the motor vehicle, such that the rotor can likewise drivethe rotor shaft and the drive member in rotation so as, in particular,to start the heat engine of the motor vehicle.

[0042] The rear bearing carries a brush holder linked electrically to avoltage regulator. In certain embodiments, the rear bearing likewisecarries a rectifier device, such as diodes or transistors of the MOSFETtype, in order to rectify the alternating current produced in thewinding 14 of the stator described below.

[0043] In a variant, the rectifier device is at a distance from the rearbearing, as described in the document FR-A-2 806 224.

[0044] The brushes of the brush holder are intended to co-operate withcollector rings supported by the rear end of the rotor shaft. Theserings are linked to the ends of at least one excitation winding of therotor. In the document FR-A-2 806 224 mentioned above, an excitationwinding is provided, and the rotor is of the claw type, that is to sayof the type featuring two toothed pole wheels defining magnetic poleswhen the excitation winding is supplied with electric current. In avariant, permanent magnets are mounted between the axially orientedteeth to increase the magnetic excitation flux.

[0045] In a variant, the rotor has salient poles, as described, forexample, in the document PCT/FR02/00037 filed on May 1, 2002, such thata plurality of excitation windings are provided.

[0046] In one embodiment, the alternator is water-cooled; its supportincluding a passage for the circulation of a cooling fluid such as thecooling liquid of the heat engine of the motor vehicle.

[0047] In a variant, the alternator is air-cooled in a known manner; therotor preferably carrying an internal fan at at least one of its axialends, the fan producing a radial and/or axial flow and being arrangedwithin the support for circulation of the air as shown in the twoabove-mentioned documents FR-A-2 806 224 and PCT/FR02/00037. Referenceshould be made to these documents for more details.

[0048] A fan is preferably provided at each end of the rotor.

[0049] In all cases, the front and rear bearings have openings for aircirculation.

[0050] In a variant, in the case where the alternator is water-cooled,the rotor can be provided with at least one fan producing an axial flow.

[0051] Referring to FIGS. 1 and 2, it will be seen that the stator for amulti-phase motor-vehicle alternator essentially includes a core 12supporting a winding 14 formed by an assembly of electrically conductivesegments, such as 16. This type of winding is referred to as barwindings. The core 12 is supported by the support of the alternator atthe outer periphery of the latter, possibly with elastic elements inbetween, as described in the document FR-A-2 806 224.

[0052] In a conventional manner, the core 12 is produced fromcylindrical metal sheets and is provided with slots or notches, such as18, distributed in a regular arrangement along the periphery of the core12 and in each of which a conductive segment 16 is inserted with anelectrical insulator 180, e.g. a mica-based insulator, inserted in aknown manner between the segments and the edges of the slots 18. In thiscase, the slots 18 are of the semi-closed type and open out at the innerperiphery of the core 12 by way of an opening whose width is less thanthat of the slots. In a variant, the slots are of the closed type.

[0053] Each conductive segment 16 has the general form of a U, the baseB of which projects from one of the large faces of the core 12 and thebranches of which are each inserted into a respective notch 18 in such away that their free ends project beyond the other large face of the core12 of the stator, as can be seen in FIG. 1. These free ends are referredto as buns and are arranged at right angles to the fans so as to be wellcooled by circulation of the air, as can be seen, for example, in thedocuments EP-A-1 043 828 and FR-A-2 806 224 mentioned above.

[0054] More particularly, and as shown in FIG. 1, for example, twobranches 20-a and 20-b of the same winding segment 16 are inserted intotwo notches 18 remote from a predetermined number of notches, in whichbranches of adjacent conductive segments are inserted.

[0055]FIG. 1 likewise shows one of the outputs of the phases. For moredetails, reference should be made to the document PCT/FR01/04147 filedon Dec. 21, 2001.

[0056] As can be seen in FIG. 2, each conductive segment has a generallyrectangular cross section and is covered with an electrically insulatinglayer to ensure that the segments are electrically insulated from eachother in the slots 18.

[0057] One of the branches 20-a of each segment 16 is inserted into aradially inner portion of a respective slot 18, the other branch 20-bbeing inserted into a radially outer portion of another respective slot18 to form at least two radially superposed layers per slot. In thiscase, assembly is achieved by threading the branches 20-a, 20-b axiallyinto the slots. In a variant, assembly is achieved by threading the saidbranches radially into open slots converted into semi-closed slots afterthe placement of the conductive segments (of the bars) by folding overmaterial, as described in the document FR-A-631 056.

[0058] As will be seen in FIG. 1, once all the conductive segments 16 ofthe stator 16 have been fitted, all the slots 18 are provided withbranches of conductive segments 16. This stage of mounting theconductive segments on the core 12 is followed by a stage in which thefree ends of the conductive segments are folded in such a way, forexample, that the free ends of the conductive segments situated in aradially outer position are folded clockwise, when considering thedirection of rotation of the rotor, and the end zones of the conductivesegments in a radially inner position are folded anticlockwise. Thesefree ends are preferably folded at an angle of 45° relative to thegeneral axis of the rotor.

[0059] To carry out this operation, for example, use is made of rotaryturrets provided with gripping notches, each intended to receive onefree end of a conductive segment, each turret being used to fold aconductive segment assembly, either in the clockwise or theanticlockwise direction.

[0060] After this assembly and this folding stage have been carried out,the mutually opposite free ends of branches situated in the same slot 18are welded, as is conventional, in such a way as to form a continuouswinding around the stator.

[0061] In the embodiment example shown in FIGS. 1 and 2, the stator isarranged in such a way as to be provided with four conductive-segmentbranches for each slot 18, forming on the outside of the body 12 twopairs of free ends 22 and 24 of conductive segments 16 spaced apart fromeach other with a view to being welded.

[0062] The arrangements described in the document PCT/FR01/04147mentioned above can be adopted.

[0063] Of course, the invention likewise applies to any otherarrangement according to which the slots are each provided with anarbitrary number of conductive-segment branches, e.g. twoconductive-segment branches, depending on the number of turns and ofphases to be obtained.

[0064] For example, the conductive segments are produced from anelectrically conductive copper wire covered with an electricallyinsulating layer of enamel.

[0065] To produce a continuous winding along the periphery of the core12, the facing free ends 22 and 24 of the conductive segments are weldedto one another. To do this, a contactless welding process is used,preferably a welding process of the electron-beam type or preferably alaser welding process.

[0066] These welding techniques are known per se. They will thereforenot be described in detail below.

[0067] However, it will be noted that these welding techniques make itpossible to achieve effective welding without carrying out a preliminarystage of stripping the corresponding free ends of the conductivesegments, the layer of electrically insulating material covering thewire of electrically conductive material being denatured in the courseof the welding process proper, under the action of the heat generated bythe welding means used, leading to fusion of the metal.

[0068] As can be seen in FIG. 3, in one embodiment, in the case where alaser beam L is used, the said beam extends parallel to the facingfree-end zones of the conductive segments 22 and 24 to be welded, thatis to say parallel to the axial axis of symmetry of the stator.

[0069]FIG. 4 shows the point of impact 200 of the laser beam on the freeends to be welded of the conductive segments.

[0070] Here, this point of impact is circular overall.

[0071] In a variant, by contrast, when an electron beam E is used, shownin the form of dots in this figure, the beam is preferably inclined atan angle A of around 45° relative to the axis of the stator.

[0072] It is, of course, possible to incline the laser beam as shownschematically in FIG. 10 relative to the axial axis of the stator, thepoint of impact 300, which is then oblong in shape, being shown in FIG.11.

[0073] This inclination makes it possible to increase the tolerances ofthe process.

[0074] In these different embodiments, the laser or electron beamproduced can be either continuous or discontinuous.

[0075] As for the stator 12, it is driven in rotation in accordance withthe arrow F in such a way as to successively present to the weldingmeans used each of the conductive-segment ends to be welded.

[0076] Thus, in the course of the rotation of the stator 12, four zonesmay be distinguished in the stator, these being designated respectivelyby the references I, II, III and IV in FIG. 3, each of which correspondsto a specific phase of the process for assembling segments.

[0077] Zone I corresponds to an unwelded zone. The free ends 22 and 24of the conductive segments are then in an unstripped form and areconsequently each made up of a wire of electrically conductive materialcovered with a layer of electrically insulating materials.

[0078] During the following phase II, two adjacent ends, which are incontact here, of conductive segments are situated opposite a weldingmeans and are subjected to the action of the laser or electron beamused.

[0079] As mentioned above, the beam can be either continuous orintermittent. When the beam is an electron beam, it can be continuous.When using a laser beam, however, the laser is preferably driven in sucha way that its operation is sequential and coincides with the stepwiserotation of the stator 12. More precisely, the laser is fired preciselyand rapidly in a rhythmical manner without the need to operate in avacuum, as in the case of electron beam welding, or in an inert gas, asin the case of TIG-type welding, which make it necessary to ensure aflow of current between an electrode and the free ends of the conductivesegments to be assembled and hence to remove the electrical installationin advance.

[0080] During welding, the laser beam is fixed relative to the core 12fitted with the facing free ends 22 and 24 of the electricallyconductive segments to be welded, this being the optimum forapportioning, in particular by acting on the duration, and concentratingthe energy of the beam without the need to preheat and strip the facingfree ends 22 and 24. Moreover, this minimises the distance over whichthe enamel on the ends 22 and 24 is modified by the heat of the weldingprocess.

[0081] This laser welding process thus makes it possible to obtain weldsof good quality and good geometry.

[0082] The laser welding process is preferably carried out in a pulsedmanner, making it possible to quantify precisely the energy used foreach weld.

[0083] This control of the energy makes it possible to ensure perfectreproducibility of the geometry of the joints between the ends 22 and 24without using any other related means.

[0084] In this case, the laser pulses last for 0.05 to 0.06 seconds, forexample. The core 12 fitted with the conductive segments is then turned,during which process the laser is inactive.

[0085] In other words, the welding means, in this case of the lasertype, is driven in a sequential manner, the beam being turned on duringwelding, then turned off between each weld.

[0086] It will likewise be noted that, in the case where an electronbeam is used, it has imparted to it a sweeping motion in such a way asto irradiate the entire welding zone delimited by the facing edges ofthe free ends of the conductive segments.

[0087] In the course of phase II, that of welding proper, the layer ofelectrically insulating material, in this case enamel, is denatured byburning. After welding (phase III), a film P made up of denatured enameldebris is thus formed in a zone subjected to the heat released by thewelding means. The height of this film is relatively small,corresponding substantially to the welding zone, the remainder of theelectrically insulating layer remaining intact.

[0088] In the course of the final phase IV, this film P is removed byany appropriate means, for example by brushing followed by a suctionphase.

[0089] A current of air is advantageously ensured between the conductivesegments of the stator below the welds to make it possible to avoidcontamination of the conductive segments by welding residues. Thiscurrent of air limits the risks of a short circuit.

[0090] In another embodiment (FIGS. 5 to 9), the free ends to be welded22 and 24 have a necked shape, as described in the document DE-A-37 04780. In this case, these ends 22 and 24 each have an angled chamfer 124of between 45° and 55° (45 °±10°) and a flat edge 125 with a width ofbetween 25% and 50% of the width of the segments 16; the faces of theends 22 and 24 which are intended to come into contact being without achamfer. These chamfers make it possible in a known manner to introducethe conductive segments easily into the slots 18.

[0091] Good results have been obtained for unstripped segments 16 with awidth equal to at least 2 mm, the enamel having a stabilising effect.The chamfers promote welding because this makes it possible to localisethe heat more effectively.

[0092] Weld seams 126 of the penetrating type with an inner trianglewhich, in this case, has a base equal to the width of a segment 16 and aheight equal to 50% of the width of the wire are obtained. The point ofthe triangle extends axially further inwards than the chamfers 124.

[0093] As can be seen in FIG. 8, there is a clearance between the twoends after welding, this clearance stemming from the modification(stripping) of the enamel during welding leading to fusion of the metal.By shortening the welding time, it is possible to obtain a weld seam ofthe type shown in FIG. 12, i.e. a shallower penetrating weld.

[0094] In this FIG. 12, a clearance due to the modification of theenamel during welding has likewise been shown.

[0095] The seam 126′ of FIG. 12 does not project relative to theconductive segments.

[0096] In all cases, these seams 126, 126′ are not very thick, as can beseen more clearly in FIG. 9, such that there is no risk of anyshort-circuiting. Circulation of air is thus promoted at the level ofthe seams.

[0097] The assembly process is economical in relation to the processdescribed in the document EP-A-1 081 831, necessitating displacement ofthe ends to be welded relative to an electric arc in order to align thewelds.

[0098] In this case, no relative movement at all is necessary by virtueof the formation of penetrating weld seams. This promotes the cooling ofthe winding 14.

[0099] In fact, a fan is installed in the abovementioned manner radiallybelow the thin welded ends 22 and 24, such that the structure of theseseams promotes the passage of air and hence good cooling of thealternator and a reduction in noise.

[0100] The alternator, which in this case is of the multi-phase type,can thus be very powerful.

[0101] It will be noted that the edges of the segments 16 are roundedhere, as can be seen more clearly in FIG. 6, in such a way that thispromotes welding.

[0102] In the embodiment in FIGS. 5 to 9, the electrical insulation 280positioned between the edges of the slots 18 and the conductive segments16 is open, as shown in FIG. 2, but are [sic] opening is adjacent to oneof the lateral edges of the slot 18 in such a way that the inner openingof the slot 18 is closed by the insulator 280, in contrast to theembodiment in FIG. 2. This improves leaktightness.

[0103] In the embodiment in FIGS. 5 to 9, the outer periphery of thebody 18 is grooved, thus forming teeth 101, in this case trapezoidal inshape, separated by notches 102. The teeth 101 face the slots 18. Thesearrangements promote the cooling of the stator while at the same timeleading to a saving of material during the production of the body 12.The body can be formed by winding a strip of material or by formingstrips of material, which are bent round. In this embodiment, the edgesof the segments are more rounded than in the embodiment in FIGS. 1 to 3.

[0104] In one embodiment, the rectangular overall cross section of thesegments is, of course, square overall.

[0105] The conductive segments are here mechanically in contact in aslot at the level of their width. The reverse is possible, all dependingon the circumferential spacing between two consecutive slots 18.

[0106] The present invention is, of course, not limited to theembodiment examples described.

[0107] Thus, in the above-mentioned manner, the assembly processaccording to the invention is applicable to the rotor of the alternator,e.g. to an alternator belonging to an electromagnetic retarder of thetype described in the document FR-A-2 627 913. In this case, the statoris traversed by the rotary shaft to be braked, while the rotor is firmlyfixed in rotation to the shaft.

[0108] The stator then forms the inductor of the machine, and the rotorforms the armature of the machine, the winding of the rotor withconductive segments being rectified by an appropriate rectifier bridgebefore being applied to the coils of the retarder, as can be seen inFIG. 2 of the document FR-A-2 627 913.

[0109] As can be seen in FIGS. 13 and 14, which correspond respectivelyto FIGS. 8 and 12, the presence of the chamfers 124 is not obligatory.

[0110] As a variant, it is, of course, possible, instead of usingU-shaped conductive segments, to use two segments, each corresponding toone branch of the U, welded together to form a U again.

[0111] In this case, each bun of the winding 14 includes welds. The twobranches of the U may, of course, not be symmetrical. For example, thearrangements described in the document U.S. Pat. No. 2,407,935 can beadopted, the connection rings being replaced by welds according to theinvention.

[0112] In FIGS. 1 and 5, the base B of the segments 16 belongs to theclosest bun of the stator to the rear bearing of the support. Thestructures can be reversed, the base then being closer to the frontbearing.

1. Process for assembling conductive segments (16) of a rotor or statorwinding of a rotary electrical machine, comprising the stages consistingin: inserting the conductive segments (16) in slots (18) arranged in acore (12) of the rotor or of the stator in such a way that the segmentsproject beyond the latter by their free ends, folding the free ends ofthe conductive segments, and welding the conductive segments (16) inpairs by their projecting free ends to form a winding around the rotoror the stator, characterised in that, the conductive segments each beingformed by a wire of electrically conductive material covered with alayer of electrically insulating material, the layer of electricallyinsulating material is eliminated, in the zone in which the conductivesegments are welded, by the means used to weld the latter.
 2. Assemblyprocess according to claim 1, characterised in that the stage in whichthe layer of electrically insulating material is eliminated is carriedout during the welding of the conductive segments (16).
 3. Assemblyprocess according to claim 2, characterised in that, following thewelding of the conductive segments, a stage in which debris ofelectrically insulating material produced during welding is removed. 4.Assembly process according to claim 3, characterised in that the stageof removing debris includes a phase in which the welded zones arebrushed, followed by a suction phase.
 5. Assembly process according toclaim 1, characterised in that the welding process is a welding processof the electron-beam type.
 6. Assembly process according to claim 5,characterised in that the general axis of the electron beam is inclinedby about 45° to the axis of the rotor or of the stator.
 7. Assemblyprocess according to claim 5, characterised in that, in the course ofwelding, the electron beam has imparted to it a sweeping motion over theentire welding zone.
 8. Assembly process according to claim 1,characterised in that the welding process is a laser-welding process. 9.Assembly process according to claim 8, characterised in that the weldingmeans is driven in a sequential manner, the laser beam being interruptedbetween two welding operations.
 10. Process according to claim 9,characterised in that the welding operation between [sic] the laser beamis fixed relative to the free ends (22 and 24) to be welded of theconductive segments.
 11. Process according to claim 10, characterised inthat the free ends (22 and 24) to be welded have a chamfer for theformation of a penetrating weld seam forming an inner triangle.